In recent years, there has been developed a technology for transferring a pattern that is called an imprinting method. The imprinting technology is also called a nano-imprinting technology and is a mold processing technology by pressing a nano-stamper (mold) in which a concavo-convex pattern of nano scale is formed to a substrate coated with a resin thin film to transfer the concavo-convex pattern to the resin thin film. The imprinting technology can perform a nano-scale processing more simply and with lower cost than photolithography or electron beam lithography in semiconductor lithography of the related-art perform.
The imprinting method is classified broadly into a thermal imprinting method and a photo-imprinting method. Among them, the thermal imprinting method is a production method of a three-dimensional molded form including: applying a thermo-curable composition on a substrate; heating the thermo-curable composition to a heat distortion temperature of the thermo-curable composition or higher while pressure-bonding a mold having a three-dimensional concavo-convex shape on the surface thereof to the thermo-curable composition to thermally cure the composition; and removing the mold to transfer a three-dimensional shape of the mold to the cured resin. The thermal imprinting method is used synonymously with an emboss method, a press method, a replica method, a transfer copying method or the like.
On the other hand, the photo-imprinting method is attracting attention as a technology capable of producing a three-dimensional molded form with high precision and low cost particularly in applications such as semiconductor lithography, fine optical parts, photonic crystals, members for a flat panel display, micro chemical chips and the like. The photo-imprinting method is a production method of a three-dimensional molded form including: using as a mold, a transparent material such as quartz; coating a substrate with a photo-curable resin; irradiating the photo-curable composition with an ultraviolet ray while pressure-bonding a mold having a three-dimensional concavo-convex shape on the surface thereof to the thermo-curable composition to photo-cure the composition; and removing the mold to transfer a three-dimensional shape of the mold to the cured resin.
As the photo-curable composition, there is a well-known non-solvent type photo-curable composition containing an acrylic resin and a photo-radical polymerizing agent (see Non-patent Document 1).
However, when the above photo-curable composition is used, there is the problem that when the molded form is released from the mold after a compression molding, the composition remains as a residual film in a part which is pressed by a convex portion, so that a desired three-dimensional molded article is difficult to be obtained. In the related-art, for removing a residual film formed in various pattern transferring technologies, the following methods have been developed:    (i) removing the composition using a reactive ion etching or the like after the mold release (see Non-patent Document 2 and Patent Document 1);    (ii) high-pressure jetting a developer containing a surfactant to the residual film after the mold release, and subjecting the residual film to an ashing treatment (see Patent Document 2) or a process for brushing the residual film (see Patent Document 3);    (iii) providing a photo-curing reaction-controlling film capable of blocking a photo-curing reaction on a mold having a concavo-convex shape (see Patent Document 4); and    (iv) providing a light shielding film in a convex portion of a mold having a concavo-convex shape (Patent Document 5). However, in the methods of (i) and (ii), the number of transferring processes increases, which leads to the elevation of the process cost. In addition, in the methods of (iii) and (iv), the mold production process becomes complex, which leads to the elevation of the mold cost.
On the other hand, for fundamentally suppressing the formation of the residual film during the transfer of the three-dimensional pattern, it is preferred that the fluidity of the composition is enhanced by minimizing the viscosity of the photo-curable composition, whereby the photo-curable composition is easily squeezed out by a mold convex portion during the pressurization. However, by lowering the viscosity of the photo-curable composition, the shape maintainability of a coating film formed after applying the photo-curable composition on a substrate lowers, which easily causes a film rupture, so that it is necessary to enhance the adhesion of the coating film to the substrate.
In the related-art, for enhancing the adhesion of a coating film formed on a substrate, there are known methods such as:    (a) forming a fine concavo-convex shape on the surface of the substrate (see Patent Document 6),    (b) as a binder of a coating film-forming material, using a binder having a functional group capable of forming a hydrogen bond between the coating film and its underlayer (see Patent Document 7),    (c) enhancing wettability of a coating film-forming material on the surface of the substrate with an alcoholic alkali liquid to suppress the coating film rupture (Non-patent Document 3), and    (d) blending inorganic fine particles in a curable composition (see Patent Document 8).However, in the method (a), there is a problem that a fine concavo-convex shape formed on the substrate surface is transferred to the molded form to lower the performance of the molded form in an application in which the molded form is utilized. In addition, in the case of using the method (b), there is a problem that the degree of freedom of the material design of the photo-curable composition with respect to the formation of the three-dimensional pattern is hindered. Further, although the method (c) can be mentioned as the most general as a method for enhancing the adhesion of the coating film to the substrate, the method (c) leads to an adverse effect in the imprinting technology application that is an object of the present invention, particularly in terms of suppression of the formation of a residual film at a mold convex portion. Then, by the method (d), it is difficult to homogeneously disperse inorganic fine particles in the curable composition, so that the inorganic fine particles agglomerate or precipitate and the fluidity of the composition lowers. Further, when such a curable composition in which inorganic fine particles are heterogeneously dispersed is spin-coated, there is caused the problem that foreign matters are observed in the coating film and the film thickness becomes heterogeneous, so that an advantageous coating film cannot be obtained and a desired three-dimensional processed form is difficult to be obtained.    Non-patent Document 1: “PAK-01” products catalogue made by Toyo Gosei Co., Ltd.    Non-patent Document 2; Hiroshima, Optical and Electro-Optical Engineering Contact, vol. 43, p. 624 (2005)    Non-patent Document 3: “Zoku jikken wo anzenni okonautameni (For safely performing the experiment, sequel)”, p. 4 (1987), published by Kagaku-dojin Publishing Company, INC.    Patent Document 1: Japanese Patent Application Publication No. JP-A-2006-39106    Patent Document 2: Japanese Patent Application Publication No. JP-A-2003-98334    Patent Document 3: Japanese Patent Application Publication No. JP-A-2003-98333    Patent Document 4: Japanese Patent Application Publication No. JP-A-2005-354017    Patent Document 5; Japanese Patent Application Publication No. SP-A-2004-304097    Patent Document 6: Japanese Patent Application Publication No. JP-A-2005-70434    Patent Document 7: Japanese Patent Application Publication No. JP-A-2002-277609    Patent Document 8: Japanese Patent Application Publication No. JP-A-2007-177194